U.S. Pat. No. 4,697,577 discloses a dual-view arthroscope construction in which the field-of-view angle is changed by moving a lens prism transversely of the arthroscope axis between a silvered and an unsilvered surface of an objective prism. The lens prism is slidingly moved from side to side by a wire arrangement.
Although the apparatus of U.S. Pat. No. 4,697,577 works, the laterally sliding lens prism and the wire actuator are delicate mechanisms and present reliability problems due to the miniscule size of the parts involved. It therefore became necessary to devise an approach allowing a much more rugged construction.